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Abstract

Previous studies have demonstrated that chitosan and its derivative, N-trimethyl chitosan
chloride (TMC) are effective and safe absorption enhancers to improve mucosal delivery
of macromolecular drugs including vaccines. Furthermore, chitosan and TMC can easily
form microparticles and nanoparticles, which have the ability to encapsulate large
amounts of antigens. Emzaloid™ technology has proven in the past to be an effective
delivery system for numerous drugs. Emzaloids can entrap, transport and deliver large
amounts of drugs including vaccines.
In this study, the ability of chitosan microparticles and nanoparticles, TMC microparticles
as well as micrometer and nanometer range Emzaloids to enhance both the systemic and
mucosal (local) immune response against diphtheria toxoid (DT) after nasal
administration in mice was investigated.
The above mentioned formulations were prepared and characterised according to size and
morphology. DT was then associated to the chitosan microparticles and nanoparticles as
well as TMC microparticles to determine the antigen loading and release. It was found
that the loading efficacy of the formulations was 88.9 %, 27.74 % and 63.1 %
respectively, and the loading capacity of the formulations was 25.7 %, 8.03 % and
18.3 %.
DT loaded and unloaded (empty) chitosan microparticles and nanoparticles, TMC
microparticles, micrometer and nanometer range Emzaloids as well as DT in phosphate
buffered saline (PBS) were administered nasally to mice. Mice were also vaccinated
subcutaneous with DT associated to alum as a positive control. All mice were vaccinated
on three consecutive days in week 1 and boosted in week 3. Sera was analysed for anti-
DT IgG and nasal lavages were analysed for anti-DT IgA using an enzyme linked
imrnunosorbent assay (ELISA).
In the study conducted to determine the systemic (IgG) and local (IgA) immune
responses it was seen that DT associated to all the experimental formulations produced a
systemic immune response. The said formulations produced a significantly higher
systemic immune response when compared to the formulation of DT in PBS.
Furthermore, the mice vaccinated with DT associated to the TMC formulations showed a
much higher systemic immune response than the mice that were vaccinated
subcutaneously with DT associated to alum, whereas the other formulations produced
systemic immune responses that were comparable to that of DT associated to alum. It was
also found that DT associated to the experimental formulations produced a local immune
response, however only DT associated to TMC microparticles produced a consistent local
immune response.
It can be concluded from the in vivo experiments that the TMC formulations, moreover,
the TMC microparticles is the most effective and promising formulation for the nasal
delivery of vaccines.